1. Field of the Invention
The present invention relates to a pattern measurement method, a manufacturing method of a semiconductor device, a pattern measurement apparatus, and a program.
2. Related Background Art
As general methods of measuring patterns, various techniques have been proposed and improved. For example, in a field of a semiconductor integrated circuit, a dimension measurement has been carried out using a critical dimension scanning electron microscope (CDSEM) in order to evaluate a fine pattern of a semiconductor. In this dimension measurement, a distance between two edge points of a pattern is only obtained. In order to evaluate a shape of the pattern from obtained results of the dimension measurement, dimensions of a plurality of portions of the pattern are measured, and an amount defined as the pattern shape has to be calculated on the basis of the measurement results. This will be described with reference to an example of an elliptic pattern shown in FIG. 25. It is to be noted that in the following drawings, the same components are denoted with the same reference numerals, and the description of the same components will be appropriately omitted.
In the example shown in FIG. 25, a dimension a in the longitudinal directions and a dimension b in the lateral directions of an elliptic pattern HP50 are separately measured, and these values or values calculated from these values in accordance with a certain calculation rule are outputted as a pattern shape. The calculation rule includes, for example, an area and oblateness of an elliptic pattern given by A=πab, e=a/b, and the like. When one or several amounts are defined as the pattern shape in this manner, there is a merit that a person who measures the pattern can intuitively and easily understand the pattern shape.
However, the above-described pattern measurement method has a problem that an accurate shape cannot be represented, when the shape of the measurement target pattern cannot be represented by a certain mathematical equation. For example, there are also patterns such as patterns HP52 and HP54 of FIG. 26 which have the same oblateness e as that of the elliptic pattern HP50 of FIG. 25 but which have mutually different areas. Furthermore, in a case shown in FIG. 25, short and long axes of the elliptic pattern HP50 agree with X and Y-axes directions of an image, but otherwise, there is a problem that short and long diameters of the elliptic pattern cannot be measured by dimension measurement in the X and Y-axes directions.
To solve the problem, it is also necessary in the measurement of the pattern diameter to carry out the dimension measurement in a direction of, for example, ±45 degrees in addition to measurement directions of 0 and 90 degrees. In this technique, however, a measurement process becomes complicated, but measurement accuracy of the pattern shape is not enhanced as expected. For example, when the diameter is measured at eight portions every 22.5 degrees from 0 degree to 180 degrees, operation of the measurement is octuplicated. However, the pattern shape is approximated as 16-gonal shape, and this is the remarkably rough measurement as approximation of a general hole pattern shape.
In addition, there is also a problem that specifications have to be checked with respect to eight measurement values as parameters which equivalently represent the pattern shape in order to evaluate the shape of the pattern.
Furthermore, for example, in fine pattern evaluation in an actual manufacturing process of a semiconductor, for example, instead of numerically describing the shape by the diameter of the hole pattern, in many cases it is necessary and sufficient only to represent a degree of difference between the patterns as an index on the basis of a normally formed pattern, or another adjacent hole pattern. Especially when an influence of an aberration of an exposure apparatus for transferring the pattern is checked, it is important to evaluate a shape difference between the adjacent patterns. In the above-described conventional method, since the dimension is measured in eight directions, a measurement time increases, and further twice the measurement time is required for measuring the shape difference between the adjacent patterns.
This problem increases a load onto a central processing unit (CPU) of a computer to carry out measurement, trouble of measurement management, and measurement time, and is additionally one of causes for an increase of cost in shape measurement.